Tony Blair's conviction that he was right to invade, to support the will of the United States, not the United Nations, divided Britain utterly.

That unwavering support for George Bush lost him friends at home, even if now, as he leaves office, it ensures him affection and respect from many of the key figures in Washington.

This is what Colin Powell, America's Secretary of State from 2001 to 2005, told the BBC: "I think Prime Minister Blair has had an enormous impact on world politics, and he certainly has had an enormous impact on the Special Relationship between the United States and Great Britain.

"He has been a friend. He has been steadfast. In the face of negative public opinion, he has stood steady, and we could always count on him.

"Well, some people say you shouldn't always have been able to count on him, but he made his own judgements, as to whether or not he should stand alongside America in some of these crisis periods.

"But having made that decision he stood firm. You never had to worry about him walking away from you, and that's what you call a friend, and that's what you call a strong leader."

Correct course?

Colin Powell's insistence that Tony Blair made his own judgements only serves to deepen the anger of some of his critics. It certainly does not look as if Tony Blair was dragged unwillingly into alliance with the American invasion.

Whatever worries he may have had about the legality of the invasion and its domestic political consequences, there's little doubt he thought, and had thought from the first, that military intervention was the morally correct course to follow.

But Colin Powell, like Tony Blair, had relied on false intelligence about Iraq's weapons when he urged the United Nations Security Council to back a speedy invasion of Iraq with a Second Resolution.

He was guilty of a good deal of spin occasionally, when he allowed himself to say that Iraq could deploy weapons of mass destruction in 45 minutes

Hans Blix on Tony Blair

In the end, the Security Council refused that endorsement, and the Resolution was withdrawn. The UN preferred the advice of their chief weapons inspector, Hans Blix. He had not found weapons of mass destruction in Iraq and argued for more time.

George Bush and Tony Blair denied the inspectors that time and Hans Blix, in his assessment for the BBC of the outgoing prime minister, is very explicit.

He accuses Mr Blair of manipulating the British people with his claim that Iraq could launch a chemical or biological attack within 45 minutes of the order being given.

"He was guilty of a good deal of spin occasionally, when he allowed himself to say that Iraq could deploy weapons of mass destruction in 45 minutes.

"Well, I think he must have realised that was an attempt to influence the public to believe more than there really was to believe. Sometimes I felt 'it takes a lot of time to build up confidence, but you can lose it in less than 45 minutes', and I think that's what he did."

Ethical dimension

To find strong public support for Tony Blair taking Britain to war, you have to go back to his first years as prime minister.

His passionate belief in intervention to save innocent lives did give foreign policy an ethical dimension.

I'm just proud to have been able to call him a friend

Colin PowellFormer US Secretary of State

Stopping butchery in Kosovo, as well as in Sierra Leone, won Tony Blair genuine applause.
Downing Street insiders who are highly critical of Tony Blair's Iraq decisions do salute him for Kosovo. Among them Sir Stephen Wall, who was Tony Blair's chief Europe adviser from 2000 to 2004.

Sir Stephen told me: "He was very much struck by what had happened in Bosnia - determined that the same thing shouldn't happen in Kosovo.

"And on Kosovo, I think Kosovo will be a significant part of his legacy. And I think for most people, they think that he did the courageous thing by saying that the international community should intervene."

European 'disappointment'

But on wider European policy, Stephen Wall thinks Tony Blair will award himself far lower marks - for his failure to move Britain decisively to the heart of the European Union.

"I think that there he is probably disappointed...I think that he was the first British prime minister for quite a long time who instinctively felt at home inside the EU.

"At the same time, the politics of the issue in Britain and the support that Tony Blair had from the Murdoch press constrained his ability to act. I think that on Europe he will, above all else, be remembered as the prime minister who did not take us into the Euro."

Blair added his voice to the Make Poverty History campaign

Where Tony Blair did find huge public support was in his campaign for Africa.

He coupled his own charisma and political power to the power of popular heroes - led by Bob Geldof.

Tony Blair also gave a voice to the idealism of millions of ordinary people inspired by the slogan Make Poverty History and the promise of wholesale cancellation of debt owed by many of the poorest states on Earth.

It all helped drive other, much more reluctant governments, to cancel debt and to increase aid, even if the long-term commitment of the rich world to deliver on all its pledges remains in doubt.

Unpredictable outcomes

But on Tony Blair and the developing world, Colin Powell is in no doubt: "The leadership he has taken on African issues, particularly during his presidency of the European Union [in 2005], where the industrial world turned its attention to the needs of Africa, will be part of his record - an important part of his record. And I'm just proud to have been able to call him a friend."

Still, that warmth cannot hide the deep anger in Britain stirred by Tony Blair's alliance with the US to invade Iraq.

It may take another 10, 20 or even 50 years to assess the full consequences of that invasion, but the consensus of present assessment is bleak.

No-one much talks about the great "Democracy Project" any more: the dream that implanting democracy in Iraq, and watching it take quick and vigorous hold, would herald the spread of government by public consent through vast swathes of the profoundly undemocratic Middle East.

Instead, it's the unpredictable outcomes - for Iraq, for the Middle East and the world as a whole - which will be Tony Blair's largest foreign policy legacy.